Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$211.63	10.309%	$233.4469	$233.45	$233.45	$233.40
Purchase #2	$60.96	7.828%	$65.7319	$65.73	$65.75	$65.70
Purchase #3	$38.57	9.657%	$42.2947	$42.29	$42.30	$42.30
Purchase #4	$165.30	8.179%	$178.8199	$178.82	$178.80	$178.80
Purchase #5	$155.57	6.629%	$165.8827	$165.88	$165.90	$165.90
Purchase #6	$111.33	10.172%	$122.6545	$122.65	$122.65	$122.70
Purchase #7	$134.94	11.785%	$150.8427	$150.84	$150.85	$150.80
7 purchase totals =	$878.30		$959.6733	$959.66	$959.70	$959.60